Statistical Mechanics
Information-Theoretic Characterization of Macroscopic Chaos Emerging from the Chemical Master Equation
Kenshin Matsumoto and Shin-ichi Sasa
Open chemical reaction networks exhibit
stochastic concentration dynamics at finite system sizes, whereas their macroscopic limit is governed by deterministic rate equations that can display chaos. In this Letter, we show theoretically that a rate of information loss constructed from two-time mutual information recovers the Kolmogorov-Sinai
entropy in the deterministic limit. We verify this result through numerical simulations of a Markov jump process for a three-species system involving seven reactions.
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Statistical Mechanics
Universal sampling of spin systems across quenched disorder
Jing Liu, Yeyuan Wu, Ying Tang et al. (+1 more)
Statistical physics extracts macroscopic laws by averaging over the many microscopic degrees of freedom of a system. Disordered systems demand a second and far harder average, one over the quenched randomness itself. The classic analytical routes, the replica and cavity methods, become uncontrolled outside mean-field or tree-like limits, and conventional numerical
algorithms like parallel tempering require expensive, independent equilibration for every disorder realization. In this work, we introduce a universal neural variational framework that amortizes inference across the disorder ensemble, eliminating both the need for per-instance Markov chain equilibration and the cost of retraining instance-specific variational ansatzes. Built on an encoder-decoder
Transformer architecture, after training once, it produces an explicit approximation to the Boltzmann distribution given previously unseen disorder realizations without further optimization. We validate this framework on 2D Edwards-Anderson models, and apply it to the random-bond Ising model, successfully capturing the Binder cumulant crossings near the Nishimori multicritical point. These results shift the object of variational inference from the single instance to the disorder ensemble, opening a route to frustrated many-body systems where instance-by-instance computation is prohibitive.
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All authors Jing Liu, Yeyuan Wu, Ying Tang, Pan Zhang
Materials Science
Interface-Controlled Phase Stability in Polymorphic HfO$_2$ Revealed by Machine-Learning Atomistic Simulations
Xudong Zhu, Junhong Li and Lixin He
HfO$_2$ exhibits rich polymorphism, and competition among different phases underpins many of its functional properties. Yet bulk free-energy relations alone cannot explain phase selection at mixed-phase boundaries, where interface orientation and structural continuity constrain collective rearrangements. Here, using machine-learning atomistic simulations and a Hf-centered local phase classification scheme, we show that crystallographic interface matching redirects phase competition and accessible transformation pathways. The M(100)/T(100) interface remains pinned as an M/T mixture throughout 3 ns simulations from 300 to 1800 K. M/PO, M/AO, and PO/AO interfaces retain two-phase coexistence up to 900 K, whereas all T/PO interfaces become PO-dominant. At 1800 K, all non-M interfaces become T-dominant, while M-containing interfaces retain a monoclinic majority. Nudged elastic band calculations reveal lower-barrier routes through interface states. For M(100)$\rightarrow$T(100), the interface-mediated route in a long
cell ($\sim$12 nm) yields a barrier of 136.03 meV/f.u., 29.2 % lower than the direct route in a short
cell ($\sim$3 nm). This difference is associated with sequential phase-front motion absent from the short
cell. These results identify phase boundaries as active participants in phase stability and transformation and establish interface orientation and crystallographic matching as variables for stabilizing metastable polymorphs and directing phase conversion in HfO$_2$.
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Strongly Correlated Electrons
Optically induced metallic state with persistent monoclinic symmetry in NdNiO$_3$
Christian Tzschaschel, Felix Utsch, Qi Song et al. (+6 more)
Understanding whether electronic and structural order remain coupled under nonequilibrium conditions is a central challenge in correlated materials. Here, we simultaneously track
metallicity and
symmetry across the photoinduced
insulator-to-metal transition in NdNiO$_3$ using time-resolved optical reflectivity and
symmetry-sensitive second-harmonic generation. We find that metallic reflectivity emerges at significantly lower excitation fluence than restoration of the orthorhombic high-temperature
symmetry. As a result, optical excitation stabilizes a metastable state that combines the reflectivity of the metallic phase with the monoclinic
symmetry of the insulating phase, revealing an optically induced monoclinic metal. Only at substantially higher fluences does the
symmetry fully recover to that of the high-temperature phase. These results demonstrate a nonequilibrium decoupling of
metallicity and structural
symmetry and establish simultaneous multiprobe spectroscopy as a powerful approach for identifying emergent phases in correlated materials.
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All authors Christian Tzschaschel, Felix Utsch, Qi Song, Spencer Doyle, Grace A. Pan, Charles M. Brooks, Julia A. Mundy, Clemens von Korff Schmising, Stefan Eisebitt
Soft Condensed Matter
Kinetics of ferritin crystal formation and melting in acoustically levitated droplets
Anita Girelli, Iason Andronis, Aigerim Karina et al. (+5 more)
Understanding
protein crystallization pathways is essential for controlling crystallization in structural biology, materials science, and pharmaceutical applications. Classical nucleation theory does not fully capture crystallization processes for several
proteins, including ferritin. Here, we combine acoustic levitation with small- and wide-angle X-ray scattering (SAXS and WAXS) to monitor ferritin crystallization in evaporating aqueous polyethylene glycol (PEG) solutions. Acoustic levitation rapidly drives the droplets through a broad range of
protein and
polymer concentrations, enabling time-resolved measurements of crystallization during evaporation. The scattering data show that ferritin
crystals form during evaporation and subsequently lose their crystalline order upon further dehydration. Varying the PEG molecular weight switches between distinct crystallization pathways: one dominated by attractive
protein-
protein interactions and another dominated by repulsive interactions and excluded-volume effects. Furthermore, we find that lower molecular weight PEG (1000 g/mol) suppresses the dehydration-induced loss of crystalline order observed for higher molecular weight PEG (6000 g/mol), providing a simple strategy for improving
protein crystal stability.
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All authors Anita Girelli, Iason Andronis, Aigerim Karina, Sampad Bag, Lennart Bergström, Tomás Plivelic, Felix Roosen-Runge, Fivos Perakis
Mesoscale and Nanoscale Physics
Enhancing charge stability of Ge quantum well heterostructures via SiGe layer composition engineering
Ding-Ming Huang, Jun-Hang Liu, Han Gao et al. (+10 more)
Composition modulation is a powerful technique for designing materials with tailored properties, fueling the development of advanced
semiconductor devices. In this work, we have implemented this technique into Ge
quantum well
heterostructures, offering a promising avenue to address the critical challenge of charge stability in
spin qubit devices. Harnessing the atomic-scale precision of molecular beam epitaxy, we have engineered the band structure of the SiGe top barrier via graded composition modulation, thereby reducing charge accumulation states at the SiGe-dielectric interface and strengthening the effective confinement to the hole gases in the Ge
quantum wells. The enhanced charge stability of composition-modulated SiGe/Ge
quantum well
heterostructures is confirmed in Hall devices, featuring an enlarged stable gate voltage range. We have further fabricated
quantum dot devices from the composition-modulated SiGe/Ge
quantum well
heterostructures and observed remarkably low charge noise with an averaged amplitude of $0.46\,\mathrm{\mu eV}/\mathrm{\sqrt{Hz}}$ at $1\,\mathrm{Hz}$—the lowest reported value for Ge
quantum wells grown on silicon. This exceptional charge stability of the
quantum dots persists in the few-hole regime, with no observable voltage drift over $\sim$hours. With reduced charge noise and enhanced energy stability, composition-modulated SiGe/Ge
heterostructures exhibit significant potential for applications in building high-performance
quantum devices, including
spin qubits with a long coherence time.
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All authors Ding-Ming Huang, Jun-Hang Liu, Han Gao, Jie-Yin Zhang, Jian-Huan Wang, Fang-Ze Liu, Xin-Yu Zhou, Yi Luo, Bin-Xiao Fu, Xiao-Fei Liu, Ji-Yin Wang, Jian-Jun Zhang, H. Q. Xu
Materials Science
Interplay of spin-lattice and electronic coupling far above Neel ordering in 2D antiferromagnetic CrPS4 and its interface manifestation
Divya Jangra, Binoy Krishna De, Mukesh Kumar Dasoundhi et al. (+13 more)
A short-range
spin correlation driven, strongly intercoupled
spin-
phonon-electronic state far above TN (~38K) is identified in the low dimensional van der Waals antiferromagnet CrPS4. Temperature-dependent Raman spectroscopy reveals
spin-
phonon coupling persisting up to T*~120K, concomitant with local
lattice distortion. The setting of vibronic progression in photoluminescence spectra suggests the strengthening of electron-
phonon coupling around T*. Furthermore, both the electrical transport and optoelectronic response also change significantly at T*. The results indicate that
spin-
phonon coupling above TN in CrPS4 originates from local
lattice distortion induced by short range
magnetic correlations which in turn enhances the electron-
phonon interaction. Furthermore, using a CrPS4/In2Se3
heterostructure, we demonstrate that the anomaly associated with the coupled degrees of freedom in CrPS4 also influences the adjacent In2Se3 layer. The
lattice dynamics of In2Se3 is significantly modified across the
magnetic anomaly of CrPS4, and the coupled dynamics is observed at T*. These interfacial manifestation opens up new possibilities for achieving correlated multifunctionalities in artificially designed
heterostructure.
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All authors Divya Jangra, Binoy Krishna De, Mukesh Kumar Dasoundhi, Sourav Chowdhury, Pragati Sharma, Kartick Biswas, Arup Basak, Dheeraj Kumar Gupta, Koushik chakraborty, Praveen Kumar Velpula, Pavan Nukala, U. Chandni, Arvind Kumar yogi, Mukul Gupta, Markus Hucker, Vasant G. Sathe
Statistical Mechanics · Cross-listed from cs.IT
Physics of Information Geometry - Part II: Small-Step Active Inference on the Probability Simplex
C. Emre Koksal and Deniz Sargun
This paper is the second in a two-part investigation of the physics of information geometry. While Part I develops a physical foundation for distributional motion on the probability simplex, the present paper studies how that framework manifests in active inference. The treatment is fully self-contained and does not require familiarity with Part I. We focus in particular on active inference through small distributional steps and the
geometric structure induced by such local motion. Starting from an initial distribution, an
agent evolves its belief state toward a final target distribution through a sequence of constrained updates. We define a relative free energy functional with respect to the preferred distribution and extend it to a relative potential energy analogous to the Helmholtz/Gibbs free-energy decomposition. The
evolution is subject to a per-step kinetic constraint expressed through the Kullback-Leibler (KL) divergence between consecutive distributions, which serves as a discrete kinetic energy on the probability simplex. Using the information-
geometric Pythagorean
theorem on KL balls, we show that sufficiently small local moves dominate large direct jumps, and that greedy maximization of free-energy reduction is globally optimal under the kinetic constraint. This leads to a sequential variational principle in which the optimal trajectory minimizes the associated Lagrangian of the optimization problem. Similar to classical mechanics, the Lagrangian takes on the form as the difference between the kinetic and potential terms, establishing a least-action principle for distributional motion on the simplex. The resulting optimal update admits a closed form as an exponentially tilted version of the current distribution toward the preferred distribution, parametrized by an inverse-temperature-like multiplier. We further extend the framework to incorporate state-dependent geodesic...
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Mesoscale and Nanoscale Physics
Fingerprints of Excitonic Collective Modes in the Two-Dimensional Electron Gas
Jakob Wolff, Silvana Botti, Lucia Reining et al. (+1 more)
The two-dimensional homogeneous electron gas (2D HEG) is a prototype system of fundamental interest that can be realized experimentally over a wide range of densities. Here, we investigate its collective charge excitations at low densities, using time-dependent density functional theory. We demonstrate that, beyond traditional plasmons, new collective excitonic modes emerge for a Wigner-Seitz radius larger than $r_{\mathrm s} \approx 1$. These excitonic modes leave characteristic fingerprints in experimentally accessible quantities, namely, asymmetric peak structures in the loss function and very strong Friedel-like oscillations in the static linear density response that increase when the system approaches a regime of instability. Indeed, at low enough densities the collective modes cross the zero energy axis, indicating an instability of the paramagnetic 2D HEG towards the formation of a charge-density-wave phase with excitonic origin. These findings provide valuable insights for the experimental detection of excitonic collective modes in tunable 2D electron systems and contribute to the fundamental understanding of many-body effects in low-density electron gases.
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All authors Jakob Wolff, Silvana Botti, Lucia Reining, Matteo Gatti
Materials Science
High-Performance Scaled P-Type SnOx Transistor by Atomic Layer Deposition with CFET Integration
Ziheng Wang, Wen He, Chen Gu et al. (+8 more)
The development of high-performance p-type oxide
semiconductors is essential for realizing complementary logic for monolithic 3D integration, yet p-type oxide
semiconductors still exhibit substantially inferior performance compared with their n-type counterparts. In this work, we demonstrate high-performance p-type SnOx transistors by atomic layer deposition (ALD), as back-end-of-line compatible devices for monolithic 3D integration. The SnOx transistors exhibit high field-effect mobility of 6.9 cm2/Vs, low subthreshold swing (SS) of 185 mV/dec, decent on/off ratio (ION/IOFF) of 1.8*104 and high bias stability. By scaling the channel length down to 80 nm, a high on-current of 38.7 mA/mm at VDS of -1 V is achieved. It is understood that precursor and reaction engineering to suppress Sn4+ component in SnOx film are the key for performance enhancement. Furthermore, a complementary field-effect transistor with ALD SnOx p-FET vertically stacking on ALD In2O3 n-FET is also demonstrated, achieving maximum voltage gain of 21 V/V at VDD of 4 V. These findings suggest ALD SnOx as a promising candidate for scaled high-performance BEOL p-type transistors.
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All authors Ziheng Wang, Wen He, Chen Gu, Kai Jiang, Liankai Zheng, Jinxiu Zhao, Zhiyu Lin, Xiangjun Liu, Di Geng, Ling Li, Mengwei Si
Strongly Correlated Electrons · Cross-listed from hep-th
Detecting one-dimensional bosonic SPT phases via twisted entropic order parameter
Kosei Fujiki, Tsubasa Oishi and Soichiro Shimamori
Entanglement asymmetry, introduced by F. Ares, S. Murciano and P. Calabrese, provides a density-
matrix diagnostic of
symmetry breaking and successfully captures the Landau data associated with a broken
symmetry pattern. However, it is by now well established that gapped
quantum many-body systems can exhibit phases which are not characterized solely by Landau
symmetry breaking. A fundamental example is a
symmetry-protected topological (SPT) phase, and the ordinary definition of
entanglement asymmetry is insensitive to this topological information. In this work we introduce a refined quantity, which we call the twisted entropic order parameter, designed to detect SPT phases from reduced density
matrices, particularly focusing on one-dimensional bosonic systems. The key ingredient in our construction is an ancilla degrees of freedom that coherently records the untwisted state and the twisted state associated to a one-ended topological defect of unbroken
symmetry, so that the enlarged density
matrix retains the charge carried by the defect endpoint. We demonstrate our proposal in concrete
lattice models and further generalize it beyond ordinary group
symmetries, establishing its ability to diagnose SPT phases. This provides a first step toward a unified
entanglement-asymmetry framework for diagnosing
quantum phases of matter.
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Soft Condensed Matter
A Phase-Field Study of Desiccation Crack Pattern Maturation under Drying-Wetting Cycles
Hiroki Fukushima and Satoshi Yukawa
The characteristic intersection angle of the desiccation crack relaxes from near \ang{90} toward \ang{120} under repeated drying–wetting cycles. However, the theoretical understanding of this relaxation is insufficient, especially the modeling of the drying–wetting cycles. Here we introduce a phase-field model of desiccation fracture, extending the model proposed in previous studies by adding crack healing and a scar effect left by past cracks. By repeating drying–wetting cycles in a finite element simulation, we find that the angle distribution develops a growing peak near \ang{120} as the cycle number increases, consistent with experiments. The standard deviation of the intersection angle from \ang{120} relaxes exponentially with a characteristic time of about 2.85 cycles. These results are consistent with experiments, except that the characteristic time is slightly smaller than the experimental value. Crack energy dominates the total energy and also relaxes exponentially with nearly the same characteristic cycle as the angle relaxation. This decay is driven mainly by a shortening of the effective crack length rather than a change in effective fracture toughness.
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Quantum Gases
Transdimensional quantum droplets in an optically trapped Bose mixture
Xiaoran Ye, Yi Zhang, Ziheng Zhou et al. (+1 more)
We study
quantum droplets in a symmetric two-component Bose mixture with interspecies $p$-wave interactions and a two-dimensional transverse optical
lattice. The
lattice drives a crossover from an anisotropic three-dimensional gas to weakly coupled one-dimensional tubes. We calculate the ground-state energy and
quantum depletion at the Gaussian level and derive their limiting forms. At $y=g_{12}/g=-0.95$, where the bare mean field is repulsive and no free-space droplet exists, the calculated bulk equation of state supports a self-bound minimum across the crossover: a negative
lattice contribution at order $n^{2}$ supplies the attraction in the three-dimensional regime, and attractive fluctuations do so in the quasi-one-dimensional regime, with the intermediate, transdimensional range described quantitatively by neither limit. The interspecies $p$-wave interaction modifies only the
spin branch. In the parameter range studied, increasing its strength lowers the
equilibrium density across the crossover, consistently with a weakening of the induced binding.
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All authors Xiaoran Ye, Yi Zhang, Ziheng Zhou, Zhaoxin Liang
Statistical Mechanics · Cross-listed from math.PR
Recurrence and transience of random walks with drift $\rho x^{\alpha}/t^{\beta}$
Ngo P. N. Ngoc and Tuan-Minh Nguyen
Menshikov and Volkov [Electron. J. Probab. 13 (2008)] studied recurrence and transience of a class of Markovian random walks on $\mathbb R_+$ whose conditional drift depends on both time and position and is of order $\rho x^\alpha t^{-\beta}$ with $\rho>0$. The case on the critical line $2\beta-\alpha=1$, with $\alpha\in(-1,1)\setminus\{0\}$, remained open. We prove recurrence in this remaining case. Furthermore, we establish recurrence and transience criteria that complete the classification for $-1<\alpha<1$ and $\beta\ge 0$, without assuming the Markov property and under weaker assumptions on the increments than those imposed by Menshikov and Volkov.
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Soft Condensed Matter
Slow Dynamics and the Geometry of Jammed Packings
Eddie Bautista and Eric Corwin
Saddle points in the energy landscape of granular packings dominate the discrete steepest descent dynamics and ultimately determine the path that an out of mechanical
equilibrium packing will follow and the resulting stable minimum that it will find. The saddle points that ultimately determine the resulting minima tend to be low-index saddle points. For models with an analytic energy landscape, such as the $p$-
spin model, the steepest descent minimization path is affected by higher-index saddle points, which pull the system towards saddle points of decreasing index before arriving at the minima. Here, we examine the steepest descent minimization path of granular packings and compare them to the $p$-
spin model. We show that the granular packing steepest descent minimization paths act like their smooth energy landscape counterparts and get attracted by saddle points. The index versus time curves for all models follow a shifted, stretched exponential. We further show that the shape parameter for the granular packings is unchanged when the energy landscape is modified to become analytic (Gaussian potential in a harmonic well) or non-local (Mari-Krzakala-Kurchan). The $p$-
spin, on the other hand, has a significantly larger shape parameter. The reason is not due to the dimensionality, packing fraction, nonanalyticity, or the locality of the
Hamiltonian of the models. The exact reason for the discrepancy in the shape parameter is \st{still} an unsolved mystery.
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Mesoscale and Nanoscale Physics
In-plane magnetic field control of anomalous Hall response enabled by magnetic anisotropy engineering
J. C. Rodriguez E., E. De Biasi, J. I. Facio et al. (+7 more)
Engineering
magnetic anisotropy provides a powerful route to control magnetization orientation and unlock emerging functionalities in opto-spintronic and current-driven devices. Beyond its role in magnetization reversal, the effective anisotropy can strongly influence the magnetotransport response, offering an additional degree of freedom to tune new device functionalities. In this work, we report a magnetotransport study of a ferrimagnetic [Tb/Co]$_{\times 5}$ multilayer grown with a Tb thickness gradient, whose wedge-shaped tilts the uniaxial anisotropy axis slightly away from the film normal. Anomalous Hall resistivity measurements from 80 K to 300 K reveal a
spin reorientation transition, while the angular dependence of the magnetotransport responses exposes the crucial role of the tilted anisotropy. A simplified macrospin model reproduces the full angular response across the transition and shows that the observed anomalous Hall effect when the in-plane
magnetic field is applied originates from the tilt of the uniaxial anisotropy axis, which supplies a built-in
symmetry-breaking mechanism, enabling in-plane field control over the out-of-plane anomalous Hall response, sign included. These findings establish tilted
magnetic anisotropy as a promising route toward Hall effect-based sensor applications and highlight Tb/Co multilayers as a versatile platform for anisotropy-engineered spintronic devices.
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All authors J. C. Rodriguez E., E. De Biasi, J. I. Facio, D. Salomoni, S. Auffret, R. C. Sousa, I. L. Prejbeanu, A. Bruchhausen, J. Curiale, L. Avilés-Félix
Mesoscale and Nanoscale Physics
A substrate booster for P-type 2D ferromagnetic semiconductor
Hai Wang, Woye Pei, Ridong Cong et al. (+14 more)
Spin transistors with its both charge and
spin properties tuned via electrostatic gating are believed capable for widespread use, which however have proven challenging due to the extreme rareness of their physical base –
magnetic semiconductors. The latter are limited within very few systems including diluted
magnetic semiconductors (DMS) and two-dimensional ferromagnetic
semiconductors (2D-FMS), and known to suffer from inadequate gate-tunability of their electric and/or
magnetic properties. Here, we show a substrate engineering paradigm by interfacing few-layered Cr$_{2}$Ge$_{2}$Te$_{6}$ (FL-CGT) with an antiferromagnetic
insulator CrOCl. Owing to the subtle interfacial charge transfer couplings, CGT can be drastically turned from an ambipolar
semiconductor into a high performance P-type
semiconductor. When cooled below the Curie temperature, the ON-OFF ratio in such substrate-boosted FMS field-effect transistor (FET) reaches 10$^{5}$ with its coercive field $H_{c}$ of
magnetic hysteresis loop tunable by a factor of more than 200$\%$, enabling {gate-assisted
magnetic switching in the prototype semiconducting
spin transistor architecture}. A crossover from critical power-law scaling to a dual power-law behaviour under heavy hole doping was further observed. Our findings {signify} an efficient interfacial charge transfer and electrically modulated
magnetic anisotropy energy supported by calculations. This high performance P-type FMS-FET system suggests that active substrate-boosting paradigm might be a powerful path for the investigation of future gate-tunable spintronic devices.
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All authors Hai Wang, Woye Pei, Ridong Cong, Xiaoyan Liu, Yuping Tian, Kenji Watanabe, Teng Yang, Takashi Taniguchi, Xiangru Kong, Weijiang Gong, Guowei Zhou, Xiaoxi Li, Hanwen Wang, Jixuan Wu, Jiezhi Chen, Xiaohong Xu, Tongyao Zhang
Materials Science
U-Shaped Fermi-Level Dependence of Point-Defect Aggregation Enthalpy in Silicon
Yin Wu, Xiao Kong and Pai Li
Point defects govern the electronic and structural behavior of silicon, yet their configuration and energy depend on both the charge state and the Fermi level (EF). Using an unbiased global structure search with first-principles calculations, we screened more than 1,500 candidate structures, covering intrinsic defects and C, H, O, N, P, and B impurities in charge states from -2 to +2. The reaction enthalpy of defect aggregation depends on EF in a U shape, being strongest where the net charge transferred during the reaction vanishes and weaker toward both band edges. This U arises because complexes are more charge-neutral than their isolated constituents, so the net charge transfer changes sign across the gap. The point where this sign change occurs is set by the transition levels of the specific defects. For typical reactions, the driving force is tunable by 0.3-0.5 eV, which shifts the
equilibrium complex concentration by five to eight orders of magnitude at room temperature. Our results make the Fermi level a practical lever for defect engineering in as-grown and irradiated silicon.
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Materials Science
Silicon Solar Cell Design for >30% Efficiency via Singlet Fission
Shona McNab, Phoebe Pearce, Pietro P. Altermatt et al. (+8 more)
Singlet fission (SF) materials convert high-energy
photons into multiple charge carriers, providing a route to exceed the efficiency limits of single-junction silicon solar
cells without many of the complexities of multi-junction tandem designs. Following the first demonstration of an SF-enhanced silicon solar
cell in 2025, there is a need to understand how SF materials can be effectively integrated into high-efficiency industrial silicon devices and translated from proof of concept to a manufacturable technology. Using coupled optical and electrical simulations, we assess the efficiency potential of several industrially relevant silicon
cell architectures combined with SF materials. Interdigitated back-contact (IBC)
cells offer the greatest potential for improvement due to unrestricted front-surface access and can achieve efficiencies exceeding 33%. However, performance is highly sensitive to front-surface passivation quality. Appropriate silicon design, particularly controlled surface doping and fixed interfacial charge, can mitigate recombination losses and relax passivation requirements for ultra-thin
exciton-transfer layers.
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All authors Shona McNab, Phoebe Pearce, Pietro P. Altermatt, Jingnan Tong, Ruy Sebastian Bonilla, Timothy W. Schmidt, Murad J. Y. Tayebjee, Bram Hoex, Alison Ciesla, Michael P. Nielsen, Nicholas J. Ekins Daukes
Materials Science
A model of grain growth in UN integrating molecular dynamics, phase-field modeling, and uncertainty quantification
Mohamed AbdulHameed, Fadel M. Nasr, Wen Jiang et al. (+2 more)
Grain growth kinetics and grain-boundary (GB) properties in uranium mononitride (UN) are investigated through an integrated multiscale framework combining molecular dynamics (MD), phase-field modeling, and surrogate-assisted uncertainty quantification. MD simulations yield GB energies for 27 symmetric tilt boundaries from 0–2000~K, which are consistent with available DFT values. The average GB energy is nearly temperature-independent below 1000~K and increases at higher temperatures. A mechanistic pore-drag model applied to the only available grain growth
dataset for actinide nitrides yields a mobility reduction factor of $s \approx 0.93$–$0.99$, statistically indistinguishable from unity, confirming that pore drag is negligible under the experimental conditions. The intrinsic GB mobility is therefore extracted directly from the effective mobility, yielding $M_0 = 2.05\times10^{-15}$~m$^4$/(J$\cdot$s) and $Q_M = 0.89$~eV. Phase-field simulations conducted from 1500–2000~K confirm normal
curvature-driven grain growth, with grain size distributions converging to the Hillert-like form. A surrogate-assisted global sensitivity analysis—combining principal component analysis, Gaussian process regression, and Sobol decomposition—reveals that the mobility prefactor $M_0$ dominates output variance at all times, followed by the activation energy $Q_M$, while the GB energy $\gamma$ contributes minimally. These results establish the first quantitative grain growth framework for UN and identify the reduction of uncertainty in $M_0$ and $Q_M$ as the highest-priority target for future experimental efforts.
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All authors Mohamed AbdulHameed, Fadel M. Nasr, Wen Jiang, Mahmoud Yaseen, Benjamin Beeler
Disordered Systems and Neural Networks · Cross-listed from cs.LG
Phases in a class of associative memories via hidden neurons
Toshihiro Ota and Masato Taki
Associative
memory in the Hopfield network is attractor dynamics in a disordered many-body system, and higher-order and exponential extensions turn its
retrieval update into softmax
attention. The
polynomial and exponential regimes have been analyzed by different methods, with no common architecture in which to ask what fixes the storage scale. In this paper we study the bipartite architecture of Krotov and Hopfield, which we call the class $H$, whose model is fixed by a Lagrangian for each layer, taking the hidden
neurons as the order parameter of
retrieval. At
polynomial load the replica method yields the replica-symmetric phase diagrams and closed-form capacities, and the crosstalk moment is common to Ising and spherical visible
neurons, so their differences come from the visible
entropy. With a softmax hidden layer the load is exponential, and a copy representation maps the thermodynamics onto random-energy-model counting, with paramagnetic, condensed, and frozen phases. Heating destabilizes
retrieval by quantized reassignments of
attention, and typical Gaussian patterns remain metastable at every load. The regimes differ in their crosstalk statistics, central-limit at
polynomial load and large-deviation at exponential load, and the class $H$ splits
retrieval into two roles, the visible Lagrangian fixing stability and the hidden one the storage scale, two axes that may also guide the design of new Lagrangians.
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Materials Science
Measuring chiral phonons
Rahul Rao, Hanyu Zhu, Nicholas Kotov et al. (+7 more)
Chiral
phonons are quantized vibrations where the atomic motion in a solid breaks improper rotation
symmetries. In many cases, chiral
phonons possess angular momenta and are therefore selective to circularly polarized light. Both fundamental and applied research efforts on chiral
phonons have been gaining increasing
attention owing to their importance in a variety of fields including spintronics,
spin-selective chemical reactions, thermal transport,
quantum information processing and biosensing, where the bi-directional
spin-
lattice coupling enabled by chiral
phonons can be harnessed in new ways, and potentially lead to new functionalities. Thus far, the studies of chiral
phonons across diverse materials platforms have evolved largely independently within these fields, but the experimental techniques are often interrelated. In this perspective, we present a detailed description, as well as advantages and disadvantages of the current approaches for experimentally measuring chiral
phonons in chiral and achiral materials. We conclude with a discussion of new methods for measuring chiral
phonons. Ultimately, this work seeks to offer an experimental guide for systematically investigating the properties of chiral
phonons in various materials systems and applications.
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All authors Rahul Rao, Hanyu Zhu, Nicholas Kotov, Thuc T. Mai, Maria F. Muñoz, Dali Sun, Jun Liu, Wonjin Choi, Renee R. Frontiera, Angela R.H. Hight Walker
Statistical Mechanics · Cross-listed from hep-th
Hao-yu Wang and Wu-zhong Guo
We investigate timelike
entanglement in
quantum field theory using spacetime density
matrices and provide a microscopic
lattice realization. For a two-dimensional free real scalar field, we extend Gaussian diagonalization methods to the generally non-Hermitian reduced spacetime density
matrix and determine its complete nonzero spectrum in the generic regular case, together with all integer Rényi moments. The real-time replica construction identifies these moments with Lorentzian branch-point twist-operator correlation functions. We test this identification against the full four-point function on a circle, boundary two-point functions with Dirichlet and Neumann boundary conditions, and massive form-factor predictions, finding quantitative agreement in both magnitude and phase across distinct causal regimes. The boundary setup exhibits a finite causally connected window in which every integer Rényi
entropy is real, showing that reality is not equivalent to causal disconnection. These results provide a microscopic
lattice foundation for timelike
entanglement and for Lorentzian twist-operator methods beyond equal-time regions.
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Mesoscale and Nanoscale Physics
Emergence of spin-orbit coupling among spin, atomic orbital, and Bloch dynamics in Janus double-transition-metal MXenes
Tetsuro Habe
We found a
spin-orbit coupling to cause a simultaneous correlation among three degrees of freedom, the electronic
spin, orbital, and Bloch dynamics in an investigation into the electronic structure of Janus double-transition-metal MXenes, Mo$_2$HfC$_2$OS and W$_2$HfC$_2$OS. In this paper, it is also revealed that the
spin-orbit coupling causes a staggered
spin configuration with a trigonal pattern around the $\Gamma$ point near the insulating gap. We developed a reduced
Hamiltonian describing the electronic states and show that the
spin-orbit coupling cannot be equated with conventional forms for a single electron in solids, LS, Rashba, and Dresselhaus couplings, even in the approximation under the low-energy and small wave number condition. Because of the intrinsic shape of the conduction band, a trigonally alternating
spin-momentum locking emerges with the
spin axis perpendicular to the layer plane. The theoretical analysis shows that these Janus materials can provide a platform for exploring the
spin-related phenomena due to the trigonal
spin-momentum locking other than Rashba and Dresselhaus types.
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Disordered Systems and Neural Networks
Irrationality Measure Controls Long-Wavelength Charge Fluctuations in Quasiperiodic Systems
Junmo Jeon and Shiro Sakai
Quasiperiodic order is characterized by irrational frequencies whose rational approximability known as irrationality measure defines distinct arithmetic classes. We establish that this arithmetic classification has direct physical consequences for long-wavelength charge fluctuations. In translation-covariant quasiperiodic systems, the infrared scaling of charge fluctuation is governed by the interplay between the irrationality exponent of irrational frequency and the large-harmonic decay of the hull charge profile: the latter determines the available charge weight, while the former controls how efficiently that weight is transferred to the infrared. Consequently, all algebraic irrational frequencies share the same arithmetic scaling, whereas exceptionally well-approximable transcendental frequencies can exhibit strongly enhanced infrared fluctuation scaling. We further prove that occupied states separated from the Fermi level by a gap stable throughout the hull contribute only an analytic infrared background, leaving the nontrivial scaling to near-Fermi states. Our results extend to general translation-covariant multi-frequency quasiperiodic systems.
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Materials Science
Hyperspin Altermagnets
Hai-Yang Ma, Yuanchang Li, Hu Xu et al. (+2 more)
The behavior of
spin quantum in k-space is key to identifying altermagnets (AMs) as the third kind of fundamental collinear magnetism. In contrast, non-collinear magnets,though abundant in nature,lack well-defined
spin quantum numbers, and the resulting
spin textures are often highly complex, which limits their potential for next-generation spintronic applications. Here we propose hyperspin, which lives in a higher-dimensional space, to address these drawbacks. Through analyzing the commutation relations between
spin and
Hamiltonian for a class of non-collinear magnets, we reveal it is a hyperspin, rather than the usual
spin, that commutes with
Hamiltonian. Unexpectedly, these non-collinear magnets should also show collinear
spin-split bands in k-space like collinear AMs. We therefore classify such non-collinear magnets as hyperspin altermagnets (HAMs), as opposed to the usual collinear AMs. Our theory elucidates the fundamental physics of AMs and HAMs and provides a framework for exploring the wide range of non-collinear magnets that may possess other kinds of conserved quantities.
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All authors Hai-Yang Ma, Yuanchang Li, Hu Xu, Shengbai Zhang, Jin-Feng Jia
Strongly Correlated Electrons
Competing Interlayer Loop Currents and Superconductivity in the Bilayer $t$-$J_\perp$-$V$ Model
Luciano Zinni, Fabricio Gómez, Jun Zhan et al. (+4 more)
The recent discovery of high-$T_c$ superconductivity in pressurized and thin-film bilayer nickelates, featuring a strong interlayer exchange coupling, and their potential similarities with cuprate
superconductors, has made this a very active topic in condensed matter physics. In the present paper we study the strongly correlated one-orbital ($d_{x^2-y^2}$) bilayer $t$-$J_\perp$-$V$ model for nickelates, where $V$ denotes the Coulomb interactions, using a controlled large-$N$ expansion at and beyond the mean-field level. Focusing on the out-of-plane
spin exchange interaction ($J_\perp$), we find that it triggers both out-of-plane $s$-wave superconductivity and an out-of-plane bond-order phase ($z$-BOP) instability. The $z$-BOP gives rise to a complex $z$-axis hopping dominated by its imaginary component, which drives out-of-plane currents and induces in-plane ones, spontaneously forming on the vertical plaquettes a loop-current state that breaks time-reversal
symmetry. Competition between this loop-current phase and superconductivity yields a dome-shaped superconducting region, with optimal superconductivity occurring near the $z$-BOP
quantum critical point. The resulting phase diagram features a pure loop-current region, a low-doping coexistence phase, a pure superconducting state at higher doping, and a correlated metallic state.
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All authors Luciano Zinni, Fabricio Gómez, Jun Zhan, Matías Bejas, Xianxin Wu, Andreas P. Schnyder, Andrés Greco